Winter is about to arrive in earnest with Brisbane forecast to record its coldest morning in nearly three years on Sunday.

The Bureau of Meteorology expects temperatures to fall to 5 degrees in Brisbane and minus 5 degrees further west this weekend.

Bureau forecaster Ben Annells said the Brisbane minimum was forecast to be 5 degrees on both Sunday and Monday, 7 degrees below average, as a result of the sort of southwesterly winds more common in August.

It will be the coldest weather in Brisbane since 2008 when the mercury dropped to 5 degrees on August 10, 4.5 degrees on August 11 and 4.1 degrees on August 12.

Brisbane's CBD temperature gauge has not hit 5 degrees in June since 2002.

"We have a fairly fresh southwesterly airstream that is being produced by deep low pressure systems over the Tasman Sea and a high pressure system coming across from Western Australia," Mr Annells said.

"That is going to dry conditions out on the weekend and as result we'll see overnight temperatures drop fairly significantly."

Mr Annells said Brisbane's western suburbs could experience temperatures below 5 degrees.

However the capital's residents should consider those further west, as the mercury is set to plummet to minus 5 degrees on the Darling Downs and Granite Belt and beyond.

Last Friday, Charleville and Roma shared the title of being the state's coldest, with the mercury falling to minus 3 degrees.

There will be some compensation for the chilly conditions however as the sun is expected to shine all weekend long, Mr Annells said.